Hey All,
Have an update here. I called Creative Steel today and spoke with Josh (one of the owners). It's a family operation, but their attention to detail seems to be above average. He listened to my situation and made recommendations based on their experience with our axle in their SRT 8 WK1. He passed on some great information, and as I suspected by looking at the pictures of the bushings, urethane is not created equal.
1. Their urethane (soft & hard durometer) is "hot poured" and degassed. It is a bit more time consuming and somewhat more lengthy of a process, but the end result is a less brittle, yet strong urethane. High quality name brand companies tend to use hot poured urethane on their top shelf products. PS- the durometer on their soft solid bushings is 70 which falls under the high side of soft if you check out a urethane hardness chart.
2. Most aftermarket companies that are smaller or larger companies that are manufacturing cheaper urethane do "cold poured" urethane manufacturing. This requires no off gassing and yields a brittle yet harder final product. Its simply mixing two components into a cast. I guarantee that the bushings I disliked from Jeep Perf were cold poured. Not saying this is outright wrong or bad, but it makes total scientific sense to me based on what I saw before and after. Also- I do not wish to offend or tell any one with cold poured urethane that it is "wrong" or not sufficient. Everyone will have their own experiences and can make their own decisions. I just to pass on the education / information I received this afternoon. That being said, cold poured urethane bushing tend to have a durometer of 90 which falls towards the hard side of the urethane hardness chart.
3. OK, after Josh gave me an education on polyurethane bushing manufacturing, he then gave me advice on what to buy based on my particular case and based on experience with their SRT8 GC test mule. Their test mule obviously makes lots of HP and needs all the stiffness for traction it can get launching 1/4 miles in AWD. So, hard durometer hot poured urethane was what worked best for performance, but admittedly transfers lots of vibration. Josh went on to explain that the upper pinion bushing in the XK/ WK1 is usually the one that fails first (which we all know). However - what I didn't know is that about 75% of the torque and associated stress IS TRANSFERRED TO THAT ONE BUSHING FIRST. Holy cow is that a stupid engineering design for a rubber bushing. The other two take way less of a beating.
4. Josh felt based on my trucks symptoms, intended usage & expectations that a full set of 3 soft durometer bushings was not necessary. He encouraged me to keep the two rubber OEM bushings installed (one on the side of housing and the other one on the front of the diff cover) especially as they are only 6 months old and take way less load i.e they should NOT be compromised this early. The upper rear pinion bushing (the one you have to drop the diff housing for of course
will be replaced with his $60 soft urethane bushing. He felt this will undoubtedly stop the shifter clunking and clunking under load at off speeds without transferring tons of vibration like a full set would, especially a full hard set like they use in the SRT8 where it is of course necessary.
I will let you guys all know how this works out after installation and a few hundred miles of test driving for good measure....
For me, this little experiment is worth it as the clunking personally drives me nuts!
Thanks,
Trevor
